The present application relates to current sensors and, more particularly, to a novel current sensor which is integratable with power switching control circuitry on a common substrate, while being insulated from current-carrying conductors.
It is well known to sense the magnitude of a flowing current by means of a current shunt or a current transformer, both of which components are relatively expensive, relatively bulky and are non-integratable with any associated electronic circuitry. It is desirable to provide a current sensor which has a manufacturing cost much lower than the current shunt or current transformer approach which is presently utilized, yet which still provides isolation from the conductor in which flows the current to be sensed, and also provides for easy interfacing with power switching and control circuitry.
Alternatives to current shunt or current transformer sensors have been proposed. One proposed alternative, described by A. J. Rogers in "Optical Technique for Measurement of Current at High Voltage", (Proceedings of IEE (Britain), 1973, Vol. 120, pp. 261-267), utilizes the Faraday rotation of linearly-polarized light under a magnetic field for the measurement of current flow on high voltage lines. Another alternative sensor, proposed by A. Yariv and H. V. Winson in "Proposal for Detection of Magnetic Field through Magnetostrictive Perturbation of Optical Fibers" (Optical Letters, 1980, Vol. 5, pp. 83-87), uses an optical fiber clad by a magnetostrictive material, such as nickel, with the magnetic field produced by a current-carrying conductor causing a strain in the fiber and effecting the phase-delay of a laser beam propagated along the fiber; an interferometric arrangement measures the phase delay and provides an indication of current flow, as described by A. Dandridge et al. in "Interferometric Current Sensors using Optical Fibers" (Electronic Letters, 1981, Vol. 17, pp. 523 and 524). Both the Faraday rotation and magnetostrictive-optical fiber approaches are relatively expensive and non-integratable with associated electronics. R. C. Gallagher and W. S. Corak have proposed, in "A Metal-Oxide-Semiconductor (MOS) Hall Element" (Solid State Electronics, 1966, Vol. 9, pp. 571-580), combining an MOS structure with a Hall-effect element for current measurement, but such devices have not been offered in the commercial marketplace and may well be too difficult to fabricate on a cost-effective basis.